Breast cancer electron intraoperative radiotherapy: assessment of preoperative selection factors from a retrospective analysis of 758 patients and review of literature

To report our experience with full-dose 21 Gy IORT in early breast cancer patients after breast-conserving surgery to define most important selection factors.Seven hundred and fifty eight patients, subjected to conserving surgery and IORT, were retrospectively analyzed evaluating most important clinical outcomes.Median follow up was 5.2 years. Results from Cox analyses defined 2 groups of patients, "suitable" (age 50 years, non lobular histology, tumour size ≤ 2 cm, pN0 or pNmic, ki67 ≤ 20%, non triple negative receptor status and G1-G2) and "unsuitable" for IORT, with a higher rate of breast related events moving from "suitable" to "unsuitable" group. The 5 year rate of IBR is 1.8% in suitable group with significant differences versus unsuitable (1.8 vs. 11.6%, p 0.005). Same differences between two groups were evidenced in true local relapse (0.6 vs. 6.9%, p 0.005) and in new ipsilateral BC (1.1 vs. 4.7%, p 0.015).In our current practice we consider the following preoperative factors to select patients suitable for IORT: age 50 years, absence of lobular histology, tumor size ≤ 2 cm, pN0 or pNmic, according to APBI consensus statement, including also ki67 ≤ 20%, non triple negative receptor status and G1-G2.